A new study shows that middle-aged white people are at high risk for suicide, as the U.S. suicide rate spiked among that group during 1999-2005.

Researchers found that white women made up the largest increase in suicides, although white men still make up the largest number of people who kill themselves.

Suicide rates were down among African-Americans and remained stable for Asian and Native Americans among that same time period.

The study and report by Guoqing Hu, PhD, from Central South University in Changsha, China, and colleagues included co-author Susan Baker, MPH, from the Johns Hopkins Bloomberg School of Public Health.

Why the increase? In a news release, Baker says researchers are not sure: "While it would be straightforward to attribute the results to a rise in so-called mid-life crises, recent studies find that middle age is mostly a time of relative security and emotional well-being."

She urges further research to "explore societal changes that may be disproportionately affecting the middle-aged in this country."

Researchers crunched numbers from data based on files from the National Center for Health Statistics on suicide trends from 1999 to 2005.

Suicide Rates

Here are the main results:

The suicide rate for white women 40-64 years old went up 3.9% per year during the study period.

The suicide rate among white men in the same age group increased 2.7% per year.

Overall suicide rates went up for whites -- 1.1% per year. Suicide rates went down significantly for African-Americans -- 1.1% per year.

Suicide rates remained stable for Asian and Native Americans.

The authors write that suicide is the fourth-leading cause of death among people aged 10 to 64.

In a news release, Baker says the results signal a change that could lead to better prevention. "Historically, suicide prevention programs have focused on groups considered to be at highest risk, teens and young adults of both genders as well as elderly white men. This research tells us we need to refocus our resources to develop prevention programs for men and women in their middle years."